Pipes consisting of asbestos cement for lining a shaft such as a well shaft typically have nominal diameters of between 800 and 2000 mm, while being up to 10 meters in length. A multiplicity of pipes of that nature are fitted together to form a pipe string, and let down into the well shaft. The connection between the individual pipes making up the pipe string is made by way of respective coupling sleeves which fit around the outside of the ends of the pipes which are adjacent to each other in regard to their end faces. The coupling sleeves which are substantially cylindrical have at least one internal peripheral groove which thus faces towards the external peripheral surface of the respective pipe end portion. German laid-open application (DE-OS) No. 32 25 901 discloses a form of pipe connection which is resistant to tensile forces acting along the line of the pipes, in which one of the two pipes which are to be joined together by the pipe connection is provided adjacent at least one of the ends thereof and on the outside thereof with a respective connecting ring consisting of glass fiber-reinforced plastic material. The two pipes are connected together by way of the connecting ring, by means of a sleeve-like member which fits over at least one pipe end and which has a peripheral groove in its internal surface. The glass fiber-reinforced plastic ring is provided with a corresponding peripheral groove in its external surface. In the coupling position therefore the internal peripheral groove in the sleeve-like member co-operates with the external peripheral groove in the ring to form an annular passage into which a flexible coupling member in the form of a rope or cable can be inserted. The rope or cable coupled member is fitted into the annular passage by way of a tangential bore which opens into the annular passage and which is provided in the sleeve-like member.
With that arrangement, a force acting on the interconnected pipes in the longitudinal direction thereof is transmitted to the sleeve-like member by way of the coupling member, namely the rope or cable in the annular passage, and from there is transmitted to the adjacent pipe by way of a second rope or cable coupling member of another pipe connection which is formed in the same manner. The sleeve-like coupling member has a casing of asbestos cement which is internally lined with glass fiber rovings or glass fiber roving cloths which are embedded in synthetic resin and which provide the internal peripheral grooves required for receiving the coupling rope or cable, possibly together with further peripheral grooves that may be required for receiving one or more sealing rings.
As will be appreciated, the fact that the longitudinal forces acting in the respective pipes are transmitted from the ring at the end of the respective pipe by way of the coupling rope or cable and the coupling sleeve gives rise at the rope or cable to force components which are directed radially inwardly in the case of the coupling ring on the pipe and radially outwardly in the case of the coupling sleeve. The radially outwardly directed components require the coupling sleeve to have a wall portion which is sufficiently strong to ensure that the sleeve is not broken open radially over a part of the axial or longitudinal extent thereof. In the known coupling sleeve referred to above, the wall portion of the sleeve is strengthened by means of an asbestos-cement casing forming part of the sleeve structure.
However, the coupling sleeves which include the asbestos-cement casing are comparatively high in weight, which means that it is necessary to use suitable lifting equipment or a suitably large labor force, for the purposes of handling the coupling sleeves.